1. Field of the Invention
The present invention relates to a medical suction tube employed to suck mucus and mucous membrane from a hollow organ of the patient's body and also pertains to a suction control apparatus for an endoscope that utilizes such a suction tube.
2. Description of the Related Art
A typical conventional medical suction tube has an on-off valve connected to the intermediate portion of the tube so that the tube is opened and closed by the valve. However, in the case where the tube is made disposable for sanitary reasons, for example, the valve which comes into contact with the sucked mucus and mucous membrane must also be disposed of after use for a single procedure and, therefore, the cost becomes considerably high.
To overcome the above-described disadvantage, there has heretofore been a prior art device, wherein a flexible tube is closed by pressing it sideward and, when the tube is released from the pressure, the tube returns to its previous open state by its own restoring force. With this prior art device, the sucked mucus and mucous membrane do not come into contact with any other elements than the tube and, therefore, it is only necessary to dispose of the tube alone after use for a single procedure.
However, this prior art medical suction tube necessitates an operation of closing the tube itself by pressing it sideward and this operation requires the application of a great deal of force continuously for a certain period of time.
It is possible to reduce the wall thickness of the tube in order to minimize the amount of force required to press the tube. However, a reduction in the wall thickness of the tube lowers the restoring force of the tube which is expected to act when the tube is released from the pressure, or may cause the tube to be closed when the suction force is applied thereto and results in a failure to effect a suction operation.
A suction control apparatus for an endoscope is usually provided on the control part of the endoscope and, in many cases, the suction control apparatus has a structure wherein a piston is reciprocatably fitted in a cylinder connected to a suction tube which opens at the distal end of the insert part of the endoscope.
In such a suction control apparatus, however, the number of parts is large and the structure is complicated and, therefore, the parts are likely to be clogged with the mucus and mucous membrane sucked through the tube. The mucus and mucous membrane are considerably difficult to wash off completely and therefore give rise to unsanitary conditions.
Under these circumstances, there has heretofore been a suction control apparatus wherein the suction tube is normally closed by pressing it sideward within the control part and, when a suction operation is to be conducted, the suction tube is opened by removing the pressure therefrom. With this arrangement, the sucked mucus and mucous membrane do not come into contact with any other elements than the tube and, therefore, washing conducted after use is facilitated. However, a great deal of force is needed to press the tube itself sidewardly so as to close it, and the operability of the prior art is therefore considerably low.
The amount of force required to press the tube may be minimized by reducing the wall thickness of the tube. However, a reduction in the wall thickness of the tube lowers the restoring force of the tube which is expected to act when the tube is released from the pressure, or may cause the tube to be closed when the suction force is applied thereto and result in a failure to effect a suction operation, as in the case of the above-described medical suction tube.